We report a theory of thermal spin pumping into proximity magnets under a
transverse-bias-driven heat flow of magnons in magnetic films when the dipolar
coupling to the magnetic gate is tuned to be "chiral". While there is no
rectification of the magnon current in the film, we predict that chirality
diverts a large percentage (50% for perfect chirality) of it into the gate.
This transverse thermal spin pumping effect can be controlled by rotating the
film magnetization and may help manage the heat flow in future magnonic
circuits.Comment: 7 pages, 3 figure